A. Field of the Invention
This invention relates to a method, apparatus and system for stretch bend forming of sheet stock to provide bent sheet stock.
More particularly, the present invention relates to stretch bend forming apparatus for stretch bend forming of simple or complex curves in sheet stock to provide bent sheet stock.
In a further and more specific aspect, the instant invention concerns a method and apparatus for stretch bend forming of corrugated or furrowed sheet stock to provide simple or complex curves in corrugated or furrowed sheet stock.
B. Prior Art
Prior art systems for forming bends in sheet stock include, for example, pan breaks and the like. While well adapted for providing abrupt bends in planar stock, these types of machines are not well adapted to providing large radius of curvature bends in planar stock. Additionally, these types of apparatus are poorly adapted to forming durable bent sheets of corrugated stock because they are not well adapted to accommodating the corrugations. When these types of bending devices are used to create bends in corrugated or furrowed stock, the corrugations or furrows are compressed, resulting in high localized stresses that in turn damage the finish of the sheet stock, result in decreased strength in the completed product and also provide poorer corrosion resistance due to the combination of damage to the finish and the effects of localized stresses and stretching of the material.
Corrugated or furrowed sheets of material are useful because the rigidity of sheets of material is improved by the presence of the corrugations or furrows. Resistance to bending perpendicular to the corrugations or furrows is also improved. Additionally, the ability to resist compressive forces directed along the length of the furrows or corrugations is also increased. All of these improvements are provided with little increased weight and result in less material being required for a specific application. This, in turn, reduces materials costs and also reduces the weight of the completed item. Examples of corrugated materials finding application in construction include aluminum and aluminum alloys and also iron and steel sheet materials. When iron sheets are employed for construction they are often zinc plated or galvanized. It is important in those cases to maintain the integrity of the galvanizing layer in order to preserve the desirable benefit of corrosion resistance. Dislocations introduced by bending and/or stretching of the sheet stock also tend to reduce corrosion resistance.
Bend forming devices adapted to handling of corrugated or furrowed sheet stock are able to provide large radius of curvature bends but do so in a way that results in substantial stretching of the sheet stock. This tends, once again, to result in high local stress of the sheet stock in the region of the bend. In addition to damage to the finish of the sheet stock resulting from stretching during the bending operation, the residual stresses tend to make the finish more susceptible to thermal cycling damage (e.g., flaking or peeling) and also tend to provide reduced corrosion resistance in the region of the bend as noted supra with respect to abrupt bends.
A feature common to such systems for bending sheet stock is a means that rigidly clamps the sheet stock during the bending process. This, in turn, promotes formation of localized stresses in the region that is bent by causing these areas to be stretched during the bending process. This also tends to increase stretching of the sheet stock during the bending process.
Accordingly, it is desirable, particularly with respect to corrugated or furrowed sheet stock that is to be bent, to provide a method and apparatus for reducing localized stresses and stretching in the region of the bend. Such apparatus and method result in reduced damage to the finish of the bent stock and also reduce the residual stresses and stretching of the corrugated or furrowed sheet stock in the region of the bend.
Further, the situations in which corrugated or furrowed sheet stock are bent are situations in which the increased strength and reduced weight of the corrugated material are desired. Especially when an optimal product design requires complex bending, it is desirable to preserve the beneficial properties of the corrugated material that led it to be selected for the intended application for which it is being prepared.
Accordingly, it is desirable to provide apparatus and methods for bending of corrugated or furrowed materials that result in reductions in the residual stresses. However, this alone is not necessarily sufficient because it is desirable to be able to preserve the finish of the sheet stock and also to reduce stretching (and risk of tearing or rupturing) of the corrugated or furrowed stock to the extent possible, while still providing the bends needed to complete the product or structure.
In order to combat these varied problems, some form of bending device is needed that provides all or many of these advantages even in the context of bending corrugated or furrowed materials. It is strongly desirable to maintain these advantages even when complex bending operations are required.
While the various mentioned prior art devices function as apparatus for shaping sheet stock, certain inherent deficiencies preclude adequate, satisfactory performance of the purpose of providing bends in corrugated or furrowed sheet stock without compromise of surface finish, without undue stretching and the resultant localized stress and also without undue compromise of the corrosion resistance properties of the material after it has been formed into the desired shape.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide improvements in bend formation in sheet stock and in bent sheet stock.
Another object of the present invention is the provision of an improved method and apparatus for bending of sheet stock and especially for bending of corrugated or furrowed sheet stock.
An additional object of the instant invention is the provision of an improved method and apparatus for providing reduced localized residual stress and stretching of bent sheet stock.
Still a further additional object of the present invention is to provide an improved method, apparatus and system for the bending of sheet stock, together with reduced surface finish damage to the sheet stock when it is bent.
And another object of the present invention is to provide an improved method, apparatus and system for bending of corrugated or furrowed sheet stock to provide complex bend shapes therein.
Still another object of the present invention is the provision of a method, system and apparatus for bending of corrugated or furrowed sheet stock to provide improved corrosion resistance in the bent corrugated or furrowed sheet stock.
Yet another object of the instant invention is to provide a method, system and apparatus for bending of corrugated or furrowed sheet stock to provide bent corrugated or furrowed sheet stock having improved thermal cycling properties.
Yet still another object of the instant invention is the provision of a method, system and apparatus for providing improvements in bending of corrugated or furrowed sheet stock.
And a further object of the invention is to provide improved bent corrugated or furrowed sheet stock having reduced stretching, reduced damage to the surface finish and having improved thermal cycling and corrosion resistance properties.
Still a further object of the immediate invention is the provision of a method, apparatus and system for the formation of simple or complex bends in sheet stock and especially in corrugated or furrowed sheeting together with improved surface finish qualities.
And an additional object of the present invention is the provision of a stretch bend forming machine that is adapted to rapid and efficient set-up in order to accommodate different styles of sheet stock to be bent thereby.
Yet a further object of the invention is to provide a new system and method for stretch bend forming of corrugated or furrowed sheeting.
And still a further object of the invention is the provision of method and apparatus, according to the foregoing, which is intended to allow the formation of complex curves in corrugated or furrowed sheet stock together with improved surface finish, reduced material stretching, reduced internal stress, improved thermal cycling properties and improved corrosion resistance.